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IAC ??????

SUBFAN

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OK....After a full tune-up, plugs, cap, rotor, wires and retimed there is still a miss at idle in the '90 Burb....

Along with the above I installed a new EGR valve and controler.

Everything was put back together correctly. The truck runs down the road smooth as glass, no problems, except for occasionally stumbling around at the ol' stop light.

Currently tried remedies are fuel injector cleaner, and a few tanks of better gas. Any other possible idea's????

Thanx on advance /forums/images/graemlins/dunno.gif /forums/images/graemlins/dunno.gif /forums/images/graemlins/dunno.gif /forums/images/graemlins/dunno.gif /forums/images/graemlins/thinking.gif
 

bckinblk

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If the iac does.nt help try replacing the throttle position sensor .. /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif
 

SUBFAN

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Wish I had the book telling me how to check these things prior to just R&R....

I like your title, AC/DC is one of my favorite all time groups, if that is the reference /forums/images/graemlins/waytogo.gif /forums/images/graemlins/woot.gif /forums/images/graemlins/waytogo.gif /forums/images/graemlins/woot.gif
 

HarryH3

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Have you checked for vacuum leaks? Our '94 was idling rough so I sprayed carb cleaner around the base of the throttle body just to check. Sure enough, the engine would stumble badly when I sprayed right near the throttle linkage. A new gasket for $7 /forums/images/graemlins/yikes.gif /forums/images/graemlins/angryfire.gif and it idles nice and smooth again. /forums/images/graemlins/thumb.gif
 

SUBFAN

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Not thoroughly, just the visual so far....

These computer motors always make me want to blame some kind of sensor first, while forgetting the 'basics' /forums/images/graemlins/ignore.gif

Thanx /forums/images/graemlins/waytogo.gif
 

bablazer73

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You can pull the I.A.C. out and clean them. They often build up carbon on the shaft and seat and won't work well. The Carbon makes the shaft sticky and won't slide in the selonoid. Some good ole carb cleaner and shove it back in!! I had to do this with my wifes higher milage 305 in her 87. When the engine gets tired(old) and the fumes(oil) strats going back through the air filter, It will go right down the passage to the I.A.C.
Whick reminds me, i have to clean the one in her S10!!

And for safety reasons, propane is a better way of checking for vacuum leaks. If you have a propane torch, Don't light it, just aim it where you think a leak might be. carb clean is ok, But highly flamable!!. I have had puddles on the intake light up! Also, if you have A/C, don't forget the vacuum chamber and ALL the servo's inside the truck. (don't want to use carb clean their)
 

bablazer73

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Oh, and as far as the T.P.S. goes. Check the voltage at idle. It shouldn't be more than .75 volts. (i think thats it) If it is high, it will run a little richer.
 

KRAZIE87K5

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GM expects an idle voltage of .540v from the TPS; +/- something like .040v.

I'm with Harry, check for vacuum.

-Dan
 

SUBFAN

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Thank you gentlemen....I will see what comes of this during the upcoming weekend. /forums/images/graemlins/waytogo.gif /forums/images/graemlins/waytogo.gif
 

Hustler

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Hey, my 90 Jimmy was having the same problems after a tune up. I guess I didn't noticed it until after the tune up. I was told to use Lucas fuel injector cleaner. Double up on what the the bottle says. Use 2 bottles per 25 gal of gas instead of 1. It worked fine for me. Good luck.
 
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